Many elongated medical devices are known that are inserted through an access pathway into a body vessel, organ or cavity to locate a therapeutic or diagnostic distal segment of the elongated medical device into alignment with an anatomic feature of interest. For example, catheters, introducers and guide sheaths of various types, drainage tubes, and cannulas are available that extend from outside the body through an access pathway to a site of interest and provide a lumen through which fluids, materials, or other elongated medical devices are introduced to the site or body fluids are drained or sampled from the site. Other elongated medical devices include many forms of medical electrical leads that bear sensing and/or electrical stimulation electrodes for sensing electrical signals of the body and/or applying electrical stimulation to the body, e.g. leads for pacing, cardioversion, nerve stimulation, muscle stimulation, spinal column stimulation, deep brain stimulation, etc. Other medical electrical leads bearing physiologic sensors for measuring pressure, temperature, pH, etc, in a distal segment thereof that are adapted to be placed at a site of interest are also known. Other elongated medical devices include guidewires that are directed through tortuous vascular pathways to locate a distal segment thereof typically within a blood vessel. A catheter, e.g. a PTCA balloon catheter for dilating constrictions in blood vessels or delivering stents and grafts or a medical electrical lead having a through-lumen are then advanced over-the-wire to the site. Other elongated medical devices include stiffening stylets that are placed into the lumens of medical electrical leads and in certain guidewires to impart column strength and stiffness to the assembly to enable transvenous advancement into a heart chamber or cardiac blood vessel.
Such elongated medical devices must have flexibility to navigate the twists and turns of the access pathway, sufficient column strength in the proximal segment thereof to be pushed through the access pathway alone, over a guidewire, or through a lumen, and the capability of orienting the distal segment and any electrodes, sensors or ports of the distal segment in a preferred alignment with an anatomical feature at the accessed site so that a diagnostic or therapeutic procedure can be completed. In general terms, the elongated medical device body must also resist kinking and be capable of being advanced through access pathways that twist and turn, sometimes abruptly at acute angles.
It is commonly the practice, particularly with guide and diagnostic catheters, to provide pre-formed bends at the junctions between segments, or pre-curved or shaped segments that are adapted to orient the distal segment and possibly intermediate segments into alignment with an anatomical feature at the accessed site. For instance, many diagnostic procedures involve placing a catheter tip into a side port and across a vascular orifice to inject radiographic fluid through the catheter lumen into the vessel. Such diagnostic catheters have historically been formed of thermoplastic materials that can be heated by being inserted within heated water, for example, and bent into a shape that the physician can use in attempting to access the vessel opening. A considerable variety of pre-formed shapes of such catheters have been developed over the years and made available for use in such procedures. Still, the physician may find that the anatomy of any given patient may require altering the pre-formed bend by heating the catheter, changing the bend and letting it cool before it is advanced to the site where it must make an abrupt change in direction.
The distal segment of the guide catheter frequently needs to be selectively deflected or bent and straightened again while being advanced within the patient to steer the catheter distal end into a desired body lumen or chamber. Various steerable mechanisms have been disclosed to steer guide catheters and other elongated medical devices, involving use of a deflection mechanism, referred to as control lines, reins, deflection wires, traction wires, push-pull wires or pull wires (herein “pull wires”), extending between a proximal handle through proximal and distal segments of the catheter body to a point of attachment of the pull wire distal end to the distal segment. More complex steerable catheters have two or more pull wire lumens and pull wires extending from the handle through the pull wire lumens to different points along the length or about the circumference of the catheter body to induce bends in multiple segments of the catheter body and/or in different directions. The deflection mechanism is manipulated to selectively deflect or straighten the distal segment and, in some cases, intermediate segments of the device body.
Exemplary multi-lumen and bilumen catheters having relatively larger delivery lumens and incorporating pull wires in relatively small pull wire lumens extending alongside the delivery lumens to selectively deflect the distal segment of the catheter are disclosed in U.S. Pat. Nos. 2,688,329, 3,605,725, 4,586,923, 5,030,204, 5,431,168, 5,484,407, 5,571,085, 6,217,549, 6,251,092, and 6,371,476, and in published U.S. Patent Appln. Pub. No. 2001/0049491 assigned to Biotran Corp. Many such steerable catheters are relatively simple, having only a pull wire lumen and a delivery lumen extending between proximal and distal lumen ports for introduction or withdrawal of fluids, or delivery of drugs or other medical devices into the body. Other steerable catheters are more complex, typically incorporating one or more distal electrode and corresponding conductor, and sometimes including other sensors, inflatable balloons, and other components.
For example, many versions of electrophysiology (EP) catheters have been disclosed that are designed to perform mapping and/or ablation of cardiac tissue to diagnose and treat abnormal tissue that induces or sustains cardiac arrhythmias and that employ deflectable distal and intermediate segments controlled by push-pull or pull wire mechanisms. During an EP ablation or mapping procedure, the guide catheter must be maneuvered through a patient's branched vasculature to advance an EP device into a patient's coronary sinus. The steerable distal end of the guide catheter is used to orient the distal tip of the EP device with respect to tissue, such as a patient's endocardium, to facilitate proper delivery of the device's RF or laser energy to the tissue. Highly complex shapes are sometimes found necessary to encircle a pulmonary vein orifice, for example, to ablate the left atrial wall tissue to interrupt arrhythmic pathways. For example, commonly assigned U.S. Pat. Nos. 5,445,148, 5,545,200, 5,487,757, 5,823,955, and 6,002,955 disclose a variety of such shapes and mechanisms for forming the shapes.
A relatively large diameter delivery lumen and relatively small diameter pull wire lumen(s) (as well as other lumens for conductors or the like) are desirable in such steerable catheters. However, the outer diameter of the steerable catheter must be minimized so that the steerable catheter can be readily advanced within the patient without trauma. Therefore extrusion techniques used to fabricate relatively large diameter, thick walled, multi-lumen fluid drainage or hemodialysis catheters and early steerable catheters, e.g., that are disclosed in the above-referenced '725 patent, are inappropriate. The walls of multi-lumen steerable catheters are necessarily thin in order to maximize the size of the delivery lumen and minimize the outer diameter of the guide catheter, while at the same time having properties that enable the catheter to exhibit column strength and pushability.
Therefore, a tubular or braided wire reinforcement is employed within at least a proximal segment of the outer wall or sheath of the typical steerable catheter to stiffen the thin catheter wall as disclosed in many of the above-referenced patents and in commonly assigned U.S. Pat. Nos. 5,738,742 and 5,964,971. The wire braid catheter wall enables torque transmission to the catheter distal end as the proximal end of the catheter outside the patient is rotated.
In the fabrication of such steerable catheters, it is necessary to extend the pull wire from a distal point of attachment proximally through the pull wire lumen extending through the steerable distal segment and the non-deflectable proximal segment of the catheter body to an exit point where the pull wire is routed through the outer sheath of the catheter body so that the pull wire proximal end can be coupled to a steering mechanism of the handle. The proximal ends of the pull wires of such steerable catheters either exit through the sidewall of the catheter body at a point distal to the catheter body proximal end, as shown in the above-referenced '030 patent and Biotran publication, or from a proximal end opening of the catheter body and are attached to a handle to be manipulated in use to induce a bend or to straighten the deflectable distal segment of the catheter body. Thus, the handle usually encloses the portion of the catheter body where the proximal end of the pull wire is exposed, and the pull wire proximal end is attached to a pull wire knob or ring that can be manipulated by the user to induce a deflection in the catheter body distal segment to steer it.
Some steerable bilumen or multilumen catheters are employed to access sites in the heart chambers, cardiac vessels or other vessels or organs of the body to deliver drugs, diagnostic agents, medical devices, and pressurized fluids, e.g., saline, to treat or cool tissue through the delivery lumen. In certain cases, electrical energy is delivered to tissue from electrodes incorporated into the catheter body or from electrodes of an electrical medical lead advanced through the delivery lumen to the site. The integrity of the delivery lumen is very important to these uses. We have found that when the delivery lumen is filled with pressurized fluid, particularly, to weep fluid from a porous irrigation tip closing the delivery lumen exit port or otherwise provide irrigation at an electrode site, the fluid can leak through the wall of the delivery lumen unless the integrity and strength of the delivery lumen wall is assured. Pressurized saline within the delivery lumen could leak into the pull wire lumen, travel proximally in the pull wire lumen, and be ejected into the handle. In the context of use of the steerable catheter body in a cautery or an EP catheter, the leakage of saline into the handle can short out electrical connections therein and/or present a risk of electrical shock to the user if the saline is in contact with the cautery or ablation electrodes.
This concern about leakage is exacerbated if the proximal exit of the pull wire from the catheter body is made through a sidewall lumen port formed in the sidewall of the catheter body distal to the catheter body proximal end. Such a sidewall lumen port is desirable when the catheter body is joined to certain bilumen catheter hubs or handles.
Once the bilumen catheter body is fabricated, it is necessary to form the sidewall lumen port through the intact catheter body sidewall before the pull wire can be inserted into the pull wire lumen (with or without a pull wire lumen liner or coiled wire sheath defining the pull wire lumen). The sidewall lumen port is made from the outside into the pull wire lumen by cutting or drilling through the outer thermoplastic layer, the wire braid, the inner thermoplastic layer, and any wire coil or pull wire lumen liner that is used (unless the incision is made proximal to the proximal end of the wire coil or pull wire lumen liner). Making such an incision is difficult, and there is a significant probability that an error may be made and that the delivery lumen liner can be punctured. The puncture may not be detectable until the delivery lumen is filled with high-pressure fluid, and the fluid leaks through the sidewall or through the pull wire lumen extending into the handle.
Even if the sidewall lumen port is successfully made, it is still difficult to route a long pull wire inserted proximal end first into the pull wire lumen distal end opening and then to route the pull wire proximal end out through the sidewall lumen port.
These fabrication steps do not lend themselves to automation and consequently require expensive, skilled hand labor, a significant expenditure of time, and can still result in high scrap at every stage of manufacturing, low productivity, and catheter products of uneven quality and reliability. Consequently, there is a need for improved manufacturing methods that can be automated at least in part and that simplifies fabrication, reduces fabrication time, cost, and scrap and that results in high quality multi-lumen catheter bodies having uniform appearance and handling characteristics. Similarly there is a need for a design of such steerable catheters that is highly robust to ensure the integrity of the delivery lumen, the reliability of use of the pull wire, and to provide consistent bend radii and shapes in the distal segments. The present invention satisfies these and other needs.